With a recent increase in the demands for enhanced efficiencies in cutting, there has been a need for a longer life of cutting tools than heretofore available. Consequently, the requirement on the properties of tool materials which has become ever more important is that wear resistance and fracture resistance associated with the life of cutting tools be enhanced. In order to obtain enhancements in these properties, coated tools are used in which an alternate film stack of coating films is disposed on a substrate.
Various techniques have been proposed to improve properties of such alternate film stacks. For example, Patent Literature 1 proposes a highly wear resistant cutting tool in which a specific metal element or a compound thereof and a specific alloy compound are stacked with a stacking period of 0.4 nm to 50 nm on the surface of a base material.
Patent Literature 2 proposes a cutting tool exhibiting excellent wear resistance even under heavy cutting conditions. This tool is such that the surface of a base is coated with 4 or more layers having an average total layer thickness of 2 to 10 μm which are in the form of an alternate stack of first thin layers of a composite nitride represented by the composition formula (Ti1-xAlx)N (x in atomic ratio: 0.30 to 0.70) and second thin layers containing an aluminum oxide phase in a ratio of 35 to 65 mass % relative to the total of the mass thereof and the mass of a titanium nitride phase, the average layer thickness of the individual layers being 0.2 to 1 μm.
Patent Literature 3 proposes a cutting tool with excellent wear resistance and welding resistance which is such that 100-5000 nm stack layers including a periodic stack of layers with thicknesses of 1 to 50 nm, and 100-5000 nm single layers are alternately stacked in 10 or more layers on top of one another on a hard base material.